The present invention relates to a semiconductor memory and, more particularly, to a technique which is effective when applied to a dynamic RAM (i.e., Random Access Memory) having its peripheral circuits of the static type.
The page mode is well known in the art as a continuous access operation in the dynamic RAM. The page mode executes the continuous read/write operations of memory cells coupled to one word line by changing a column address signal in synchronism with a column address strobe signal CAS, while the word line is being selected by a row selector, to sequentially switch data lines. There is also known in the art a static column mode, in which a column selector is constructed of a static type so that the continuous read/write operations of the aforementioned memory cells coupled to the word line may be executed by changing the column address signals, while the word line is being selected, to sequentially switch the data lines.
The above-mentioned page mode can carry out continuous access at a relatively high speed because address signals fed from the outside are incorporated by using the column address strobe signal as a clock. However, the page mode makes it necessary to feed a clock signal from the external terminals. The latter mentioned column static mode makes the continuous access possible merely by changing the column address signal. However, the column static mode is caused to have a relatively slow operation speed by the skew (i.e., the changing timing difference of the address signal) of the address signal fed from the external terminals. In other words, the column selecting operation is effected in accordance with that one of the address signals of multiple bits which will change most slowly. Thus, the two modes both have merits and demerits, and the dynamic RAM of the prior art has functions in either of the modes.
Incidentally, a dynamic RAM having the aforementioned continuous access function can be referred to in either pp. 169 to 193 of the Magazine "Nikkei Electronics" issued on July 18, 1983 by NIKKEI McGRAW-HILL (which generally discusses high integration one MOSFET D-RAMs) or the "Hitachi IC Memory Data Book" issued in Sept. 1983 by Hitachi, Ltd. (which particularly shows both page and static column modes).